Cyclopentane, a solvent and blowing agent having a basic formula of C.sub.5 H.sub.10, is typically produced in a two column and hydrotreating unit system. The conventional process for production of cyclopentane includes: (1) cracking dicyclopentadiene (DCPD) in a distillation column or other reaction vessel; (2) recovering cyclopentadiene (CPD) as liquid distillate from the distillation column; and (3) hydrogenating CPD in a hydrotreating unit. The resulting product is fed to a cyclopentane recovery column wherein cyclopentane (CYC5) is recovered as a liquid distillate. This process is characterized by the following primary reactions: EQU DCPD.fwdarw.2 CPD EQU CPD+H.sub.2 .fwdarw.C.sub.5 H.sub.8 EQU C.sub.5 H.sub.8 +H.sub.2 .fwdarw.CYC5
Part of the CYC5 may be sent to the first reactive distillation column to be used as a diluent to minimize CPD polymerization reaction in the upper section of the column.
This process requires a hydrotreating unit and two distillation columns, as shown in FIG. 1. FIG. 1 depicts a standard hydrogenation process employed in the art. This prior art process for the formation of CYC5 employs a multi-component system generally referred to by reference numeral 10. System 10 includes hydrotreating unit 12, first distillation column 14 and second distillation column 16. First distillation column 14, hydrotreating unit 12, and second distillation column 16 are linked in series by conduits 61 and 20, respectively.
Initially, DCPD is fed via conduit 22 into first distillation column 14, where it is cracked according to the following reaction: EQU DCPD.fwdarw.2 CPD
Preferred distillation conditions are a temperature of about 465.degree. F. (240.degree. C.) and a pressure of 8 psig (0.16 MPa). The resulting CPD is recovered as an overhead vapor stream and heavies are taken as bottoms via conduit 58. These heavy by-products can be removed from system 10 via conduit 59 or can be recycled through reboiler 66 to the bottom section of distillation column 14. The overhead vapor stream is transferred to condenser 54 via conduit 18. The CPD condensate is taken from condenser 54 via conduit 55, where it is either recycled to the top portion of distillation column 14 via conduit 57 as a diluent to minimize CPD polymerization reaction in the upper section of the column or to hydrotreating unit 12 via conduit 61 for further hydrogenation.
Hydrogen is fed via conduit 24 into hydrotreating unit 12, preferably in the form of H.sub.2 gas, such that it comes into contact with the CPD received via conduit 61. The CPD is then hydrogenated to CYC5 in hydrotreating unit 12 according to the reaction set forth below: EQU CPD+2H.sub.2 .fwdarw.CYC5
This reaction is typically carried out at an elevated operating pressure (i.e.,&gt;200 psig). Following the reaction, various separation steps are necessary to disengage the unreacted H.sub.2 from the hydrocarbon product. The resulting product is then transferred to second distillation column 16 via conduit 20. In second distillation column 16, CYC5 is recovered as a liquid distillate, and part or all of the CYC5 liquid distillate is removed overhead via conduit 60. Optionally, a portion of the CYC5 liquid distillate or a portion of the liquid from conduit 20 may be recycled to first distillation column 14 via conduit 62 to be used as a diluent (alone or in conjunction with liquid CPD) to minimize CPD polymerization reaction in the upper section of column 14 and to control the temperature increase in hydrogenation. Heavy by-products are removed as bottoms from second distillation column 16 via conduit 64. As such, substantial operating costs are incurred to maintain the three distinct reaction vessels. In addition, initial capital costs are high, and processing times are extended.
Conventional processes for the production of cyclopentene (with cyclopentane produced and recycled as an impurity) from dicyclopentadiene are disclosed in U.S. Pat. No. 4,048,242 (Lauer et al.). The Lauer et al. patent discloses a multi-vessel reaction process that is subject to the same cost and time limitations as the foregoing prior art process.
British patent application GB-A-2273017 (commonly owned with the present application) discloses the manufacture of cyclopentane from dicyclopentadiene by cracking the dimer in a heat exchanger and hydrogenating the monomer to form cyclopentane in a closed loop batch reactor at a temperature below 175.degree. C. The effluent is then fed to a flash drum separator and to a distillation column and fractionation column [pp. 10-11].
British patent application GB-A-2271575 (also commonly owned with the present application) discloses the production of cyclopentane from dicycloalkadiene by similar methods, wherein cyclopentane is added as a diluent in the manufacture of additional cyclopentane.
Accordingly, a need exists for an improved, simplified, more efficient process for the production of cyclopentane.
It has been suggested in the past to apply catalytic distillation to a wide variety of processes such as butene isomerization (see U.S. Pat. No. 2,403,672 to M. P. Matuzak); the hydrolysis of low molecular weight olefin oxides to produce mono-alkylene glycols (see U.S. Pat. No. 2,839,588 to A. S. Parker); and the production of methyl tertiary butyl ether (MTBE) (see U.S. Pat. No. 3,634,535 to W. Haunschild). Catalytic distillation is only now emerging as a commercially viable hydrocarbon conversion and petrochemical processing tool.
Advantages attributed to the catalytic distillation concept, wherein reaction products are continuously separated from the reactants and removed from the reaction zone by fractional distillation performed concurrently with the reaction, include a decrease in the capital cost of the plant needed to perform the process, the ability to achieve a higher degree of conversion, and the ability to perform processes which formerly were performed only in a batch type operation on a continuous basis. These advantages result from performing the reaction in a separation zone capable of removing the reaction products from the reactants and catalyst. Hence, it is only necessary to provide one primary vessel and the reaction is not limited by chemical equilibrium.
A further advantage of the catalytic distillation process is that there is no need for a high pressure hydrogenation step and all the increased capital and processing costs associated therewith.
The present inventor has developed a unique one step process which is capable of producing a high yield of cyclopentane with high selectivity in a single catalytic distillation column. This process also avoids thc need to recycle product as diluent to minimize CPD polymerization reaction.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawings.